The induction of tyrosine aminotransferase (TAT) mRNA by glucocorticoids cyclic AMP and protein synthesis inhibitors is being investigated in vivo in fetal liver explants and isolated rat liver cells in culture. As part of this study, the isolation of TAT mRNA is underway. Rat liver polysomes are being enriched for TAT synthesizing ribosomes from which TAT mRNA will be isolated. The purification scheme involves a combination of pyridoxamine phosphate affinity chromatography followed by conventional RNA purification techniques ( sucrose density gradient centrifugation and gel electrophoresis). Purified TAT mRNA will be used as a template for the synthesis of a complementary DNA hybridization probe to quantitate TAT mRNA sequences in the experiments outlined above. A survey of the domain of the glucocorticoid and cyclic AMP regulated genes in the liver cell is also underway. Liver mRNA prepared from rats treated with glucocorticoids or cycic AMP is used to direct the synthesis of hepatic proteins in the reticulocyte lysate protein synthesizing system. Translation products are displayed and quantitated by one or two dimensional electrophoresis to determine changes in specific mRNA activities in response to the steroid hormone and cyclic AMP.